<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 100px;
            height: 100px;
            background-color: blueviolet;
            /* 隐藏 */
            /* display: none; */
        }
        
        div:hover span{
            /* background-color: chocolate; */
        display: inline;
        }
        span{
            /* display: none; */
            background-color: cyan;
            float: left;
            margin-top: 100px;
        }
    </style>
</head>
<body>
    <div>
        hello
        <span>123</span>
    </div>
    
</body>
</html>